Adding an image to your content, regardless of it's a blog, book, email newsletter, or website, isn’t just a suggestion — in this day and age, it’s a requirement. Images add a wealth of depth and is the bait that potentially grabs the wandering eyes of those just passing by. However, finding a compelling image that is royalty-free and completely legal to use can be a tad bit difficult. (And no, you can’t just Google Image Search your way out of this unless you’re looking to spend a little time in the big house.)

A site I frequent to brush up on my graphic design skills called TutorialBlog posted an awesome list of 25 stock photo sites, both free and paid. Take a look before you go on your next image search.

A few of my favorites freebies made the A-list on TutorialBlog's list, including Free Range, Stock Xchng, and Every Stock Photo (really awesome), but there are a couple of paid sites that didn't make the cut that are worthwhile to mention.

iStockPhoto: With 4,725,000 photos online, iStockPhoto is one of the biggest players in paid stock photos. Yes, it is a paid site, but when I do not have success finding what I need on one of the free alternatives, iStockPhoto usually comes through strong. With pay-as-you-go credits costing a buck and a half each, it isn’t cost prohibitive… then again, it’s always hard to argue with free.

Getty Images’ Creative Express: Let's say you run multiple blogs or even an entire blog network that gets updated very frequently, and you're burning through tons of stock photos on a daily basis. If this sounds like you, Getty Images’ Creative Express offers a pretty good chunk of photos that are available based on a yearly subscription instead of on a per-picture basis. There’s a database of 200,000 royalty-free images that gets updated with 1,000 new photos every month, and you’re free to download up to fifty images per day. Here’s the catch: The cheapest subscription costs $1,999 for one year.

Swing by TutorialBlog for the full list of 25 stock photo sites, and if any of you out there have any favorites that aren't on the list, be sure to let me know in the comments below.

TutorialBlog — 25 Places to Find Awesome Stock Photos — Free and Cheap!